<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <script src="https://cdn.jsdelivr.net/npm/vue/dist/vue.js"></script>
</head>

<body>
    <div id="app">
        <p>{{x}}</p>
        <input v-model="x">
    </div>

    <script>
        var vm = new Vue({
            el: "#app",
            data: {
                x: '',
            },
            watch: {
                x: function () {
                    alert("您的电脑遭受更改！！！")
                }
            }
        })
    </script>
</body>

</html>